The electric shower also seemed pretty optimistic. I live in an area with about 50°F/10°C ground temperature and my 14.4 kW water heater can just keep a relatively efficient shower head flowing at a comfortable temperature.
This one is resistive (tiny and cheap to purchase) but will be just an emergency-backup shower once my home renovations are done.
The house is getting a split-system air-to-water heat pump with an indirect tank for domestic hot water, so it should cut that down substantially (the unit maxes out at around 3kW input but likely will run longer to recover/preheat).
